"I think it's a good thing that they're in the market," said Carol Carpenter, the general manager of Trend Micro's consumer division. "We look forward to the competition ... and I think Microsoft's targeting of developing countries and the unprotected is a good approach."

Microsoft has pitched Security Essentials, which replaced the now-defunct for-a-fee Windows OneCare, as basic software suitable for users who can't, or won't, pay for security software.

Not everyone, however, agreed with Carpenter.

"Security Essentials won't change anything," said Jens Meggers, Symantec's vice president of engineering. "Microsoft has a really bad track record in security," he added, ticking off several ventures into consumer security that the giant has tried, including Windows Defender, an anti-spyware tool bundled with Windows Vista and Windows 7; the released-monthly Malicious Software Removal Tool; and OneCare.

"Like OneCare, Security Essentials is a poor product," said Meggers. "It has very average detection rates. And now they've decided to go for the free market, but that's a very crowded market. There's not much room to grow there."

In a company blog, another Symantec employee called Security Essentials a "rerun" of OneCare , and said: "At the end of the day, Microsoft Security Essentials is a rerun no one should watch."

It's no surprise that top-tier security vendors like Trend Micro and Symantec dismissed Security Essentials today. They did the same thing last year, when Microsoft announced the upcoming demise of OneCare and said it would ship a free, streamlined product. At the time, a Symantec executive said it was a capitulation by Microsoft, which was tacitly admitting it couldn't compete .

But Meggers' take today was even more bearish. "We don't like the notion of 'basic,'" he said. "That makes me very worried, because the risk on the Web today is far too high for 'basic.' Tossing a bunch of little basic tools into the computing environment doesn't make it safe."

Even Carpenter had some unkind words for Microsoft. "It's better to use something than to use nothing, but you get what you pay for," she said. "But I don't think it will worry the main security vendors. If I were a free, focused security company, trying to get my upsell over time, like AVG [Technologies], then I'd be concerned."

Symantec's Meggers also wondered what took Microsoft so long to come up with Security Essentials. "It takes them an entire year to remove features from OneCare, to make something even worse than OneCare?" Meggers asked. "I could have done that with three developers in three months."

And that's a good clue that Microsoft won't be able to keep up with the likes of Symantec, Trend Micro and McAfee, Meggers added. "Look how long it took them to build it. Security needs constant innovation. When was the last time that Microsoft innovated?"